1. Field of the Invention
The present invention relates to a cooling apparatus of an air-cooled engine which includes a cooling fan fixed to a crankshaft and a fan housing surrounding the cooling fan.
2. Description of the Related Art
In order to cool a cylinder and a cylinder head of an air-cooled engine, typically, the air-cooled engine is equipped with a shroud covering the cylinder and the cylinder head. The shroud circulates cooling air delivered from the interior of a fan housing along the outer circumferential surfaces of the cylinder and the cylinder head. Japanese Patent Application Laid-Open (JP-A) No. 06-42347 discloses the above configuration.
In addition, in order to improve the cooling efficiency in the cylinder head, Japanese Patent Application Laid-Open (JP-A) No. 2001-241355 discloses the air-cooled engine which includes a cooling apparatus having a shroud and a cooling air passage passing into the cylinder head.
In the former conventional art, the cylinder and the cylinder head are cooled from only the outer circumferential surfaces thereof. Therefore, when an engine rotational speed is low so that the amount of the cooling air from a cooling fan is small, a portion or location to become hot in the cylinder head, e.g., the vicinity of an exhaust passage or a forming wall of a combustion chamber, cannot be cooled sufficiently.
In the latter conventional art, since the cooling apparatus has the cooling air passage in the cylinder head in addition to the shroud, the cooling effect in the vicinity of the exhaust passage in the cylinder head is improved. However, when the cooling air passage is simply formed in the cylinder head, it is difficult to supply a large amount of the cooling air to the cooling air passage. Thereby, the cooling air passage cannot be used efficiently. In the latter conventional art, the inlet area of the cooling air passage is increased to ensure the amount of the cooling air.
The present invention is related to a cooling apparatus cooling an engine body comprising of a cylinder and a cylinder head, and an object of the present invention is to provide the cooling apparatus of the engine which is capable of increasing the coolability of each location in the cylinder head and reducing the weight of the cylinder.